I Figured it out

In 1990 Preludes had the B21A1 For the 4WS Models and the modles with ABS, Since he didnt state that he has 4WS we can cross that out, We are stuck between the B20A3 and the B20A5, Since it is not Fuel Injected i feel that he has a 1990 Prelude S model because it is Carbed

You have the B20A3 at least in the states.